They have innumerable cases in which they swap out your skills for other skills. I'm certain they could have a duel situation in which you are swapped to weapon skills approximately like those of your current weapon, but balanced for 1 vs. 1, and avoiding the rock-paper-scissors class issue. There are other details to hammer out (what about trait effects, what about outside interference from mobs, etc.), but it is something that could be done.
That said, it is more work than just flipping some "PvP allowed" switch if they want to do it right, as explained above. I figure (hope?) they'd prefer to wait and do it right, if they intend to allow dueling.

In the past, I've tried fighting the mobs and ended up dying (laugh, you know you want to), then decided not to bother trying to fight them again.

If you open the present while the mobs are present, more won't spawn, even if there was only one left, so fighting two sets shouldn't be an issue. Thus, the best practice would be to leave one monster alive at each spawn location.

The recourse against this consists primarily of getting unhappy and complaining about it, so +1 unhappy complainer here.

I voted 1. No and 2. Yes, partly because I didn't feel like trying to explain a depends right away, and because I'm not really sure.
My thoughts are that a standard gear treadmill or random loot hunts could be a good thing... in their own area of the game. I'm pretty sure this has come up earlier in the thread, but at 60 pages, I'm not interested in finding it.

I've played Diablo 2 and various impersonators and found them enjoyable enough that I can't say that a loot game is a bad thing, but it's not what I play Guild Wars 2 in particular for. A subsection like this Fractals thing that could work as a separate PvE subgame (a similar idea to SPvP) that was a kind of miniature Diablo 2/Torchlight-ish game would be a neat addition and could be a place for gear to expand, possibly with some leveling of balance so everyone starts from the same space in it.

However, in the main game, with standard dungeons, maps, story, and WvW, I'd like to be able to get maximum equipment fairly easily and then focus on playing the game because it is fun and engaging.